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Second tiny asteroid spotted before it hit Earth

By Jeff Hecht

The first new asteroid identified this year didn’t last long. Asteroid 2014 AA was spotted by a telescope early New Year’s morning, and fizzled up over the Atlantic Ocean a day later.

2014 AA is only the second incoming object astronomers have tracked before it hit the Earth – and they almost missed it. The first such object, 2008 TC3, was discovered on 6 October 2008 about 20 hours before it became a fireball over Sudan.

Astronomers were not so lucky with 2014 AA. Like 2008 TC3, the new asteroid was discovered with an automated telescope in the Catalina Mountains north of Tucson by the University of Arizona’s Mount Lemmon Survey. The survey automatically tracks moving objects and calculates preliminary orbits, and then posts the data to a network of astronomers for follow-up observations.

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Holiday arrival

But 2014 AA’s holiday-period arrival meant it nearly slipped by unnoticed. With only 90 minutes of automatic observations recorded, Gray calculated the object’s orbit in the evening of 1 January and realised it was on a collision course with Earth. He had insufficient data to pinpoint the time and place of impact, but preliminary analysis of infrasound observations has since narrowed it down to around 0200 GMT in the mid-Atlantic, says Steve Chesley of NASA’s Jet Propulsion Laboratory in Pasadena, California.

Objects of 2014 AA’s size hit Earth every few months, and are too small to pose a threat to the planet. But tracking their motions through the atmosphere could help astronomers recover the pieces that survive, says Peter Jenniskens of the SETI Institute in Mountain View, California, who led the effort to collect meteorites from 2008 TC3 and the Chelyabinsk meteor.

Although 2014 AA is probably lost to the sea, learning to track others like it could have big payoffs for science. “It’s like a low-cost sample-return mission,” he says.